chore: set up pnpm workspace tooling

Root package.json with workspace scripts, pnpm-workspace.yaml, shared
tsconfig base, ESLint flat config, Prettier, editorconfig, .nvmrc, and
.env.example covering LiveKit/Gemini/GitHub/Atlas/Voyage.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,26 @@
+# Copy to .env and fill in. Never commit .env.
+
+# --- LiveKit (realtime transport) ---
+LIVEKIT_URL=
+LIVEKIT_API_KEY=
+LIVEKIT_API_SECRET=
+
+# --- Gemini (vision + voice) ---
+GEMINI_API_KEY=
+GEMINI_VISION_MODEL=gemini-3.5-flash
+GEMINI_LIVE_MODEL=
+
+# --- GitHub (state fusion + PR action) ---
+GITHUB_TOKEN=
+GITHUB_REPO=owner/name
+
+# --- MongoDB Atlas + Voyage (continual-learning memory) ---
+MONGODB_URI=
+VOYAGE_API_KEY=
+
+# --- Backend server ---
+PORT=8787
+
+# --- Frontend (Vite — must be VITE_ prefixed to reach the client) ---
+VITE_LIVEKIT_URL=
+VITE_BACKEND_URL=http://localhost:8787